1. Field of the Invention
The present invention relates to a heat exchanger tube for condensing steam by means of cooling air with an upper steam supply and a lower condensate discharge.
2. Description of the Related Art
Heat exchanger tubes of this type are usually combined in groups or rows and are coupled to other heat exchanger tubes operated as dephlegmators to form air-cooled condensers. In this connection, the heat exchanger tubes operated as dephlegmators particularly have the purpose of preventing the danger of freezing.
In accordance with the prior art, the heat exchanger tubes operated as dephlegmators, i.e., wherein the condensate flows in a counter-current flow to the steam, are arranged separately from the heat exchanger tubes operated in a co-current flow, i.e., wherein the condensate flows in the same direction as the steam, and the excess steam from the heat exchanger tubes operated as condensers is conducted through collection chambers and pipelines from below into the heat exchanger tubes operated as dephlegmators, or alternatively, the excess steam is allowed to flow through a collection chamber from below into the heat exchanger tubes operated in a counter-current flow. All heat exchanger tubes are arranged in a condenser. This condenser can be combined with additional condensers, particularly in a roof-shaped configuration.
Although the conventional principle has basically proved to be successful, it must be pointed out from practical experience that, in the past, it was always necessary to make compromises particularly with respect to the condenser/dephlegmator ratio. These compromises were due to different weather conditions prevailing over the course of a year, the maximum quantity of steam to be processed, and also the configuration of the heat exchanger tube groups in relation to the different ventilators provided for these groups.
In addition, in accordance with the prior art, pipelines are required for conducting excess steam from the heat exchanger tubes operated as condensers into the separately arranged heat exchanger tubes operated as dephlegmators. Moreover, frequently the phenomenon called "swallowing" of condensate in the heat exchanger tubes operated as dephlegmators must be observed. This phenomenon occurs when the steam velocities when entering the heat exchanger tubes operated as dephlegmators are still so high that the condensate flowing downwardly in a counter-current flow in these heat exchanger tubes is held up in the manner of an umbrella or buffer or this condensate column may even be pressed further upwardly. This "swallowing" phenomenon significantly reduces the efficiency of a condenser.